Steve 65

I have a hissing noise coming from under my dash when I accelerate/decelerate and apply the brakes.Hissing noise continues for approx 5-10 secs after vehicle is turned off.

Any Clues? - I suspect a seal from the brake booster where it penetrate's thru the firewall.

Appreciate if anyone can offer ideas how to fix this without buying a new brake booster (brake booster seems ok as I still have brakes and no warning lights have appeared).

Part details and where I can purchase them on line (reputable)would also be great - local MB dealer stated that I have to replace the whole booster at a cost of $2500 (Aust).

acurry13

oops, hit the wrong button.... anyway, if the noise is coming from under the dash by the brake pedal, it is a seal inside the car on the brake booster. You will need to access the booster from the inside, pull back the "bellows" cover between the brake pedal and the booster. You will see the seal in question. It is a bugger to get back into place, fits kind of like a grommet and is a fairly low durometer ...(if you don't have any mechanical ability, you may take a while to figure it out)... finagle the seal back into place (I used a little Mobile synthetic grease on the seal/grommet as this grease doesn't degrade rubber). Once you get that seal back into place, the hissing sound will stop.

Just to rehash, my vehicle was hissing when I released the brake and continued slightly as I was driving, and would stop when I applied the brake. The brakes worked fine as there was enough vacuum to maintain the the brake function...just an annoying hissing sound.

Wow!!! I ran across many threads on this site as well as others with the same symptoms that mentioned that they took the vehicle to the dealer or mechanic and they claimed that the booster was bad and undoubtedly charged big $$$ to replace the booster when actually only fitting the seal back into place.

Hopefully, this will help someone that is experiencing these symptoms.

Let's keep helping each other and please..NO MORE SUGGESTIONS TO TAKE THE CAR TO THE DEALER OR MECHANIC! That's not why we are on this site and is common sense if you can't figure the issue out.

Mertek71

acurry13...... I have the same symptoms with my 00' ML320 and with your advice I inspected the seal above mentioned
. "Booom", you hit the bloody nail on the head, after closer inspection, I noticed the seal was split and with the engine running, I placed my finger on the split area of the seal and the noise immediately stopped.
To confirm this was the issue, whilst holding pressure on the split area of the seal, I pressed the brake pedal a number of times with my other hand and no hissing sound what so ever was heard.
I will order a new seal and replace next few weeks......... will post results on completion of the job regarding issues along the way.

Cheers Guys

mihir_d

Wow! My 2000 ML320 at 171k miles has been doing that, the past 3 months & I was like...what the hell?

I thought, maybe there is a pressure leak in the HVAC & air is hissing through one of the vents but I could never correlate the hissing sound to the placement of the HVAC vents. Then I thought the HVAC vent in the footwell is doing it, but the hissing continues after the car is dead stopped & that perplexed me.

Now I know what it is! I will check my brake booster seal over the coming weekend. Thank you all for the posts!

Mertek71

Hi guys,........ I spent about an hour last nght removing the brake booster seal in question and taken a few pic of it for your information.
Will take the seal to my local MB parts supplier in the next few days and see what I can find out in regards to price and availabilty.

Will keep you posted.

Maj. Dundee

Save yourself a trip to the dealer. M/B does not sell anything on the internals of the booster. You will have to look at the markings on the seal and search on-line for a rebuilding kit, if there is one.

What are all the markings and numbers on the seal?

sumo2002

Thanks to Mertek for the info.
My 2002 Kompressor coupe has just developed this problem (hissing). Everyone's input has been very helpful to me so far. I'd like Mertek to follow up on the repair of the booster seal. Also, my instrument display is unreadable on sunny days. Dealer wants $450 to clean it and doesn't know whether cleaning will fix the problem--may have to buy a new one.

With these two major issues--brake booster seal and instrument cluster--I can't decide whether to invest and keep the car. I love the car and don't really want to get rid of it, but everything MB is so $$$ !

Thanks to everyone for your input!

Maj. Dundee

You are posting on the wrong forum and you should be asking your questions there.

https://mbworld.org/forums/c-class-w203-3/

But hissing on the inside indicates replacement of the brake booster.

On the cluster problem you don't say what's unreadable, but try to turn the knob to full intensity.

Mertek71

Sorry Guys,
Have been off line for a bit, anyway took the seal to my friends at the local MB spares and they advised me that the seal cannot be purchased
on its own, as you said Maj. Dundee the brake booster would have to be replaced...

However that said, they did give me some info on the numbers on the seal ( 03.7718-5018.1 ATE). They advised me to look on the net, possibly ATE (manufacturers of the brake boosters) and see what you can come up with.
In the meantime, for a temporary measure, as I needed the vehicle back on the road asap, I glued the spit with a rubber glue. Making sure the seal was free of grease and dirt before gluing, I soaked the seal in a wax and grease remover fluid for about 10 min and wiped it clean using a clean rag and dried it using compressed air.

Using rubber grease, I have reinstalled the seal and it seems to be doing the job, it took a little while putting it back in but with patience, it finally went in.
I know this may seem a bit rough , but will do for now until I can track a source for the seals. no noise from the pedal at this stage touch wood and driving the vehicle daily.

P.S rumour has it that the seals are used in other European manufactured vehicles Volvo, Renault.... will investigate further.

Peace

Madd_Scientist

I had this problem in 2008, and replaced the brake booster in my '99 ML430 with a 2003 brake booster from a recycling place, and now it's doing the exact same thing. UGGGH. What is it with these stupid seals? Hopefully someone can figure out a way of ordering these.

paperplane94

see my brake booster seal thread...

jayniepena

How do I get into the brake pedal area?

paperplane94

https://mbworld.org/forums/m-class-w...part-help.html

jbservices

Genuine MB parts 30 - 50% of the retail. RequireVin No
for more info jbservices@live.com.au

gbucyk

As noted in the posts I experienced the exact same problem of the gasket tearing. By removing the under dash bessel you can gain access to the brake area. Remove the brake pedal and you'll have full access to the cylinder that enters the cab from the booster. Fold back the ribbed cover of the cylinder and gently pull out the rubber gasket. Once removed wipe clean and I then used "Permate Ultra Gel Bond" to join the gasket back together. I then put a small coating around the tear area with "3M Black Super weatherstrip and gasket adhesive". I let set for a couple of hours and it seemed to be holding. I then slipped the gasket back over the cylinder and started to push back into the surrounding hole. I started on one end and worked my way around. One it was starting to trap I took a wooden paint stick and pushed hard on the outside working my way around. I found the paint stick long enough to give working room to apply good pressure and not sharp to further damage the gasket. Once set I rolled back the ribbed cover and assuring the air holes at the end were still able to allow airflow as mentioned in one of the posts. Everything is back together and so far so good. The experience however proves that if this doesn't hold I could go to a wrecker and pull the seal off another and just replace it. Best of luck, no use in spending $700 for a new booster if this works...

BV7753

I just invested 1093 dollars to replace my brake booster after having the troublesome hissing noise. However it is strange that the hissing began after having my brakes replaced - is it possible they did some harm to the booster when they replaced my brakes???? I too enjoy my vehicle but it is averaging 1k dollars every 3-4 months for a repair of some sort......Kia is sounding real good right about now..

mihir_d

As much as I am enjoying my 00 ML320 ownership at 190K miles, is not just headed to becoming a money pit :-(

I did the AC compressor and steering rack leak repair this season, and a 3rd major repair is already starting to pop up. At this rate, am seriously considering dumping it at 200K miles/15 yrs....and move on...

I thought, MBs were lifetime investments...guess not..15 years might be EOL...a Honda or Toyota or for that matter Hyundai or Kia might easily outlive 200K miles without giving such expensive repairs.

And yes, air bags also expire at 15 years of age...did you know that?
Technically, the air bags must be replaced...which is like $3K..

davemv

However that said, they did give me some info on the numbers on the seal ( 03.7718-5018.1 ATE).


My number is 03.7718.5016.1. Note 16 not 18. Did anyone find a replace seal anywhere>

davemv

My number is 03.7718.5016.1. Note 16 not 18. Did anyone find a replace seal anywhere?

spoofhopper

Hi did you ever track down a seal online? Thanks!

davemv

I found one in Poland but will not ship to the US.


Boaster also is used on Volvo (S60?) the French autos.


Do note my auto is a SL 500.


Got my rebuilt for 175 in CA. Believe it was Power Brake Exchange.

davemv

"The sound clearly stops when the brake peddle is applied and starts again once it's released. "


This is not the case with my hiss. It only hisses when the brake is applied. It this normal. I know the booster dumps vacuum pressure on one side when the brakes are applied. The above sounds like a seal leak to me.

Maj. Dundee

No it is not normal. You must buy a new booster or a used one and install it.

Do not even consider fixing or replacing the seal.

rokauf

Hi
Have the same problem hissing noise. Is there somenone there that has step by step pictures on how to repair this hissing noise. And from i understand i cant be repaired by the inside of car not by the inside of the hood? Just dont feel like spending big bucks on this seal problem when it can be done almost nothing.

thanks guys

davemv

I lived with CELs for two years. Finally traced it to brake booster leak. Replaced with used one for $75. Lasted a year and leaking again. Sent booster to Power Brake Exchange in Bell Gardens, CA for $175 rebuild. Reinstalled and still had leak. Called PBE and was told to call their San Jose location. They told me to return it to them. They repaired and returned to me. Installed and no leak. Have driven it for a month now and put 2000 miles on the auto.

It is a royal pain to removed and install the first and second time. Third was not that bad.

Having looked at my failed seals, I do not believe they can be replaced, assuming you can find the seal (I don't believe this is possible either). For sure not with the booster installed in the auto.

98 SL500 and 90 300 SL